Lecture 15 Flashcards
Microbial Growth Factors & Factors Affecting Growth (26 cards)
Binary Fission
form of asexual reproduction.
prok. cell division into genetically identical daughter cells.
very rapid
Spectrophotometer
measures the amount of light absorbed/ transmitted by a sample at specific wavelengths.
commonly used to estimate cell density in a culture by measuring optical density (OD).
growth curve lag phase
no increase in # of living cells
growth curve log phase
exponential increase
growth curve stationary phase
plateau
(death and division equal)
growth curve death/ decline phase
exponential decrease
factors that effect microbial growth rate
moisture, nutrients, temp, oxygen, habitat, pH, radiation, pressure
glycerol as a media source
very simple
TSB as nutrient source
tryptic soy broth
very complex medium
high quality
exponential growth formula
Nt = N0 * 2^n
(# of cells after period of time = initial # cells * 2^# of doublings)
microbial exponential growth
usually not happening.
happens under optimal conditions.
our immune systems work to stop it.
solving for the amount of doublings
log2(Nt/N0)
specific growth rate
k = ln2 / td
high = fast
m. tuberculosis td
~24hr
e.coli td
can be 20 min
copiotrophs
organisms in high nutrient enviros (fast-growing)
oligotrophs
organisms that thrive in low nutrient areas (slow-growing)
microbial growth differences from animal/ plant growth
- about increase in # of cells in pop. as opposed to size and complexity of an organism
- asexual reproduction
- rapid
- usually only need simple nutrients … can occur in extreme/ diverse enviros
- distinct phases (not so continuous)
quorum sensing
bacterial ability to sense they are living in a dense community
when they sense each other they typically change behaviour via gene expression
“gang up” on host, move away or “turn on” special genes
bacterial “persister” state
way of potentially surviving antibiotic treatment
(why finishing course of antibiotics is crucial)
growth optimum
“goldilocks zone”
area of highest growth rate
ex. a specific pH
niche for different factors (temp, light, salinity, etc.)
Danger Zone (temp)
temp. optima for mesophiles (most human pathogens) 5-60 degrees celsius
oxygen availability in our gut lumen…?
anoxic!
ecological niche
defines how an organism fits into an ecosystem.
an area catered to factors of growth optima
